Usain Bolt and Yohan Blake both win their 200m semi-finals

Jamaican Usain Bolt hardly had to break sweat as he coasted into the men's 200 metres final where he will bid for an unprecedented Olympic sprint double-double.

Bolt, 25, will be joined in Thursday's gold medal showdown by compatriots Warren Weir and his most likely title rival Yohan Blake, as well as America's one representative Wallace Spearmon.

"I'm ready. This is my favourite event so I'm looking forward to it," Bolt told reporters after blitzing the first 100 metres to allow a gentle jog on the home straight for a heat- winning time of 20.18 seconds.

"You can't work too hard, you've got the finals. That was the aim, you can't push too hard."

The world's fastest man sped to the 100m and 200m titles in Beijing in 2008 and on Sunday secured the former event once more in scintillating style. Victory in Thursday's final would make him unquestionably the sport's greatest ever sprinter.

Asked if he could break the 19.19 seconds world record he set in Berlin in 2009 Bolt said: "It's a possibility. I can't say but the track is fast so it's going to be a good race."

Although Spearmon, who finished third in Beijing in 2008 but was then disqualified for stepping out of his lane, is likely to battle it out with former European champion Christophe Lemaitre for bronze, Bolt did not rule out a Jamaican 1-2-3.

"It's going to be hard. Wallace Spearmon is there and he's been there before," said Bolt, who even managed a smile to camera once he was in the blocks at the start of his race.

"There's a lot of people there who are going to come and try and spoil the party so we'll see," he said, adding that he had managed to do some skipping in the warm-up area having had his rope confiscated before Sunday's final.

Blake, this year's fastest man, also looked impressive, running a strong bend before easing down for the night's best time of 20.01, with Spearmon and Lemaitre in hot pursuit.

"We had a tough one. We couldn't jog 20.1 (seconds) like some other guy. We were running," Spearmon said.

European champion and this year's Olympic 100 metres finalist Churandy Martina of the Netherlands also qualified.